Quest Portal
"Quest Portal is the virtual tabletop for Game Masters who want to boost their storytelling and be confident about the games they run. Create memorable stories, characters and visuals and bring them to your game with ease."
https://roll20.net/
"Easily create characters, organize games, purchase content, find players, and customize your story for your group – all in your browser."
This is a repost, since I don't want it to be buried under the more recent links
Software, online services, physical objects - anything that might help DMs and players in their sessions.
Some rules: